Conventionally, vehicle-mounted device such as a navigation apparatus performs dedicated short range communication with a roadside apparatus installed on a road by utilizing DSRC (Dedicated Short Range Communication) or the like. The vehicle-mounted device can receive information provided by a center apparatus through the roadside apparatus. More specifically, two-way communication between the vehicle-mounted device of the vehicle and the roadside apparatus is possible only while the vehicle is within a communication range of the roadside apparatus. During this period the center apparatus distributes various kinds of content information such as advertising information through the roadside apparatus.
In some cases, emergency information such as accident or disaster information is included in the content information. Since it is necessary to sufficiently attract the attention of the user to the emergency information, conventional vehicle-mounted devices output a warning sound upon receiving emergency information. For example, some vehicle-mounted devices determine the existence of a dangerous object using a sensor, and make a warning announcement to that effect (for example, see Patent Document 1). There are also vehicle-mounted devices that output a warning sound (buzzer sound, music, voice, or the like) upon receiving an emergency radio wave (for example, see Patent Document 2), and vehicle-mounted devices that lower the brightness of a display unit upon determining that emergency information is contained amongst a plurality of kinds of information (for example, see Patent Document 3).
According to the method disclosed in Patent Document 1, the reproduction time of a warning announcement is shortened or the output switches to a buzzer sound depending on the degree of urgency. According to the method disclosed in Patent Document 3, the brightness is changed according to the degree of urgency. It is thereby possible for the user to determine the degree of urgency of emergency information.
Patent Document 1: Japanese Patent Application Laid-Open No. 2006-107148
Patent Document 2: Japanese Patent Application Laid-Open No. 2003-132494
Patent Document 3: Japanese Patent Application Laid-Open No. H11-120491